Your Catalog table needs a primary key field to uniquely identify each record in catalog. (I wouldn't use description for that) That said, your conditional value list would need this relationship:
cash_estimate::Category = Catalog::category AND
cash_estimate::type = catalog::type AND
cash_estimate::item = catalog::item
For details on how to set up a value list using such a relationship, see these links:
Forum Tutorial: Custom Value List?
Knowledgebase article: http://help.filemaker.com/app/answers/detail/a_id/5833/kw/conditional%20value%20list